Problems: Reduction in performance; fire; water damage; higher energy costs; mold throughout the house.
Trouble signs: System cycles on and off frequently to keep to a thermostat setting and/or trips circuit breakers. Natural gas flames are yellow or orange rather than blue. Corrosion/rust spots or leakage from water heater.
What you can do: Replace air filters every one to three months to improve performance. Experts recommend that a water heater that's 12 or more years old should be replaced, partly due to the danger of bursting. Replace it earlier if you see corrosion or leaking. Consider a new HVAC system if repairing it is at least one-third the cost of replacement.
What it may cost: Air filters cost $2 to $15. $100-$200 for a professional inspection and cleaning of HVAC system.
What you can save: Energy waste, premature replacement of costly units, repair of flooding damage. Water heaters start at $350; forced-air furnaces cost $2,000 to $4,000, and central air conditioning units start at around $2,000. Clean filters can lower energy consumption by 5 to 15 percent.
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